Construction, recreational, and work vehicles, which have flexible endless ground engaging belts for support and propulsion of the vehicle, generally utilize smooth surface drive wheels and similar idler wheels to engage and frictionally drive the flexible belts. Sufficient tension is necessary between the drive wheels and the belt, and between the idler wheels and the belt, to ensure efficient rotation of the belt and to provide effective stopping of the vehicle when the wheels are braked. Various mechanisms have been used to develop the requisite belt to wheel tension including fluid powered cylinders and compression springs. The prior art has also disclosed mechanisms providing that a portion of the vehicle weight can be used to provide some of the required tension between the flexible belt and the wheels.
One type of such a device is shown in U.S. Pat. No. 2,998,998, issued to J. H. Hyler et al. on Sept. 5, 1961. In this patent, a portion of the vehicle weight is transferred to a front wheel supporting mechanism through a cantilevered spring beam and an associated arm. The arm is connected to a rigid link, which link carries the front wheel supporting axles. The rigid link also carries a cylindrical member having a pivot axis. As a portion of the vehicle weight is applied to the beam and arm, the wheel axles are pivoted about the pivot axis in a direction away from the rear wheel axle. Rubber bushings tightly engage the cylindrical member and are torsionally deformed during the pivoting of the front wheel axles. As the front wheel axles pivot, the distance between the front and rear wheels increases and track tension is increased.
Although the above-noted track tensioning device does provide for tensioning the track in response to supporting a portion of the vehicle weight, a considerable portion of the vehicle weight is supported by the non-moveable rear wheel axle. Since the front and rear axles are secured together by a connecting arm, a rubber bushing must be twisted or deformed in order to allow the front wheels to pivot or rotate relative to the rear wheels. The total movement of the front wheels would appear to be limited by the twisting action of the rubber bushings. The disclosed vehicle is a self-powered vehicle, intended to push or pull other non-powered implements. Therefore, the total weight of the vehicle, which is supported in part by the load responsive device, is not intended to vary appreciably.
The present invention is directed to overcoming one or more of the problems as set forth above.